A. Not for the first time (remember the Maze peace and reconciliation centre?) Sinn Fein and the DUP are at loggerheads, each accusing the other of 'bad faith' over the implementation of welfare reform.

Q. And what might this latest spat mean?

A. Potentially, the slow unravelling of the Stormont House Agreement (SHA) hammered out by the five main parties at Christmas in which welfare reform was a key component. If that falls apart, it could mean the collapse of the Assembly and Executive and fresh elections a year earlier than planned.

Q. So what is this latest row all about?

A. Sinn Fein says the DUP has welched on commitments to build in provisions in welfare legislation which would have protected some claimants - among them children with disabilities, adults with severe disabilities, and the long-term sick. The DUP insists all parties were aware of the implications of the SHA and it remains committed to full implementation.

Q. Did this row come out of the blue?

A. Yes. The Assembly was meeting yesterday for the final stage of the legislation and Social Development Minister Mervyn Storey was finalising his address when Sinn Fein called a press conference less than an hour before the sitting.

Q. Was there was no sign of this coming?

A. If you want to be wise after the event, one section of Martin McGuinness' speech to the party's ard fheis in Londonderry at the weekend referred to "The welfare protections... no matter how difficult the implementation process may get, we will not - under any circumstances - tolerate any retreat from them."

Q. But don't the parties meet regularly?

A. The five party leaders now meet every week but Mr McGuinness also revealed he waited for three hours for a meeting with the DUP last Friday which did not happen.

Q. What was the upshot yesterday?

A. Mr Storey yesterday withdrew the legislation, allowing breathing space for the respective parties to calm down and examine the clauses in greater detail. But the clock is ticking, with the carrot of retrieving half of the £140m further fine the Treasury is imposing for their failure to implement welfare reform so far.

Q. And what is likely to happen now?

A. Secretary of State Theresa Villiers has given an undertaking to meet as many of the parties as possible today but she has also emphasised the seriousness of the situation. There is no confirmation of direct talks between the DUP and Sinn Fein as yet.